antlr 重写规则的输出 [英] antlr rewriting output of a rule
问题描述
我正在尝试编写一个 antlr 脚本,其中规则 1 有一个子规则规则 2.我在规则 1 上使用 StringTemplate.
I am trying to write an antlr script where in, rule1 has a subrule , rule2. I am using StringTemplate on rule 1.
我想做的是在规则1消耗/使用之前重组规则2匹配的文本.我该怎么做?
What I want to do, is restructure the text matched by rule2 before it is consumed/used by rule1. How do I do that ?
options{
output=template;
}
rule1 :
begin sub-rule2 end ';' -> meth(body={rule1.text})
sub-rule2 :
sub-rule3
| sub-rule4
| sub-rule5;
这里的meth"是字符串模板调用
here "meth" is the stringtemplate call
如果说子规则 4 匹配select * from dual;",我希望将其传递给 rule1#sql (select * from dual);".
If say sub-rule 4 matches "select * from dual;", I would like this to be passed to rule1 "#sql (select * from dual);".
这是我的实际代码,我希望与 select_statement 规则匹配的语句包含在#sql()"中,并在stats"列表中传递给meth"模板的body"属性:
Here is my Actual code I would like the statements matched by the select_statement rule to be wrapped in '#sql()' and to be passed in "stats" list to the "body" attribute of the "meth" template :
body
@init {
List stats = new ArrayList();
} :
BEGIN s=statement{ stats.add($s.text); } SEMI ( s=statement{ stats.add($s.text); } SEMI | pragma SEMI )*
( EXCEPTION exception_handler+ )? END ID? -> method(modifiers={"public"},returnType={"void"},name={"execute"},body={stats})
;
statement :
label*
( assign_or_call_statement
| case_statement
| close_statement
| continue_statement
| basic_loop_statement
| execute_immediate_statement
| exit_statement
| fetch_statement
| for_loop_statement
| forall_statement
| goto_statement
| if_statement
| null_statement
| open_statement
| plsql_block
| raise_statement
| return_statement
| sql_statement
| while_loop_statement
)
;
sql_statement
: (commit_statement
| delete_statement
| insert_statement
| lock_table_statement
| rollback_statement
| savepoint_statement
| select_statement
| set_transaction_statement
| update_statement )
;
select_statement :
SELECT swallow_to_semi
;
SELECT : 'select';
swallow_to_semi :
~( SEMI )+
;
推荐答案
您可以像这样具体定义规则可以返回的内容:
You can specifically define what a rule can return like this:
sub_rule2 returns [String x]
: sub_rule3 {$x = ... }
| sub_rule4 {$x = "#sql (" + $sub_rule4.text + ");";}
| sub_rule5 {$x = ... }
;
现在 sub_rule2
返回一个 String x
你可以这样使用:
Now sub_rule2
returns a String x
which you can use like this:
rule1
: ... sub_rule2 ... -> meth(body={sub_rule2.x})
;
注意 sub_rule2.x
.
您还可以创建一个自定义方法来检查要添加到 List
的文本是否以 "select "
开头,如下所示:
You could also create a custom method that checks if the text to be added to the List
starts with "select "
like this:
grammar YourGrammarName;
options{
output=template;
}
@parser::members {
private void addStat(String stat, List<String statList>) {
// 1. if `stat` starts with "select ", wrap "#sql(...)" around it.
// 2. add `stat` to `statList`
}
}
body
@init {
List<String> stats = new ArrayList<String>();
}
: BEGIN s=statement { addStat($s.text, stats); } SEMI
( s=statement { addStat($s.text, stats); } SEMI
| pragma SEMI
)*
(EXCEPTION exception_handler+)? END ID?
-> method(modifiers={"public"},returnType={"void"},name={"execute"},body={stats})
;
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